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Innate immune sensing of cytosolic chromatin fragments through cGAS promotes senescence

ABSTRACT: Cellular senescence is triggered by various distinct stresses and characterized by a permanent cell cycle arrest. Senescent cells secrete a variety of inflammatory factors, collectively referred to as the senescence-associated secretory phenotype (SASP). The mechanism(s) underlying the regulation of the SASP remains incompletely understood. Here we define a role for innate DNA sensing in the regulation of senescence and the SASP. We find that cyclic GMP-AMP synthase (cGAS) recognizes cytosolic chromatin fragments (CCFs) in senescent cells. The activation of cGAS, in turn triggers the production of SASP factors via Stimulator of interferon genes (STING), thereby promoting paracrine senescence. We demonstrate that diverse stimuli of cellular senescence engage the cGAS-STING pathway in vitro and we show cGAS-dependent regulation of senescence upon irradiation and oncogene activation in vivo. Our findings provide insights into the mechanisms underlying cellular senescence by establishing the cGAS-STING pathway as a crucial regulator of senescence and the SASP.

ORGANISM(S): Mus musculus

PROVIDER: GSE100102 | GEO | 2017/06/20

SECONDARY ACCESSION(S): PRJNA390720

REPOSITORIES: GEO

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Project description:Alzheimer's disease (AD) is a severe neurodegenerative disorder. Clinical trials to identify agents to treat AD have failed, and its underlying molecular pathology and etiology remain elusive. Neuroinflammation is thought to play a key role in the progression of AD. Emerging evidence has identified lower Nicotinamide adenine dinucleotide (NAD+) levels as a major factor in neurodegeneration, especially in AD. NAD+ is an important metabolite in all human cells, as it is at the convergence of many central processes in cellular and mitochondrial maintenance, including DNA repair and mitophagy (the degradation of damaged mitochondria). Our previous work found that treatment of 3xTgAD mice with an NAD+ precursor, nicotinamide riboside (NR), can improve key AD features including tau phosphorylation and learning deficits in mice. Here we used the APP/PS1 AD mouse model to interrogate the effect of NR on neuroinflammation. Microarray analysis revealed major changes in pathways and genes associated with inflammation and the APP/PS1 mice had lower NAD+ levels than WT mice. Thus, seven months old mice were treated with NR for five months and their NAD+/NADH ratio increased. Brain neuroinflammation decreased as determined by decreased activation of astrocytes and microglia, decreased pro-inflammatory cytokines and chemokines in the brains of the APP/PS1 mice. NR decreased neuroinflammation by lowering the NLRP3 inflammasome and NF-κB pathways. NR also attenuated DNA damage and apoptosis in the AD mouse brains. NR dramatically decreased senescence in the hippocampus and cortex of AD mice, relative to controls. Recent studies suggest that cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) activation are associated with DNA damage and senescence. cGAS-STING was activated in AD mice and decreases after NR treatment. Suggesting that NR can diminish neuroinflammation and senescence through the cGAS-STING pathway. NR treatment also greatly improved cognition and synaptic function in the APP/PS1 mice. We propose that the cGAS-STING pathway should be evaluated as a potential novel therapeutic target in AD.

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Innate immune sensing of cytosolic chromatin fragments through cGAS promotes senescence

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